# 定义鸟的类
class bird:
    def fly(self):
        print("鸟在天上飞")

# 定义飞机的类
class aircraft:
    def fly(self):
        print("飞机在天上飞")

# 定义哮天犬
class xtq:
    def fly(self):
        print("哮天犬在天上飞")

def fly(obj):
    obj.fly()

fly(bird())
fly(aircraft())
fly(xtq())

